Shimabara Peninsula is a cool 30-minute ferry ride from Kumamoto New Port on an air conditioned ferry which takes both cars and passengers (those on foot can take a bus from Kotsu Center). The small town, known as “the city of water”, has long had close connections with Kumamoto; it was the last refuge for rebels seeking refuge during the Shimabara-Amakusa Rebellion (島原･天草の乱, 1638), when Amakusa Shirō rebelled against the local daimyo’s efforts to prohibit Christianity. https://en.wikipedia.org/wiki/Shimabara_Rebellion Today, several bukeyashiki (samurai houses, 武家屋敷) draw tourists, These houses are fronted with narrow canals from which the residents once drew water. In 1978, the town hit upon a further attraction: they stocked these canals with koi (the colorful ones are known as nishikigoi, 錦鯉, inspired by a nearby house dating to the late Meiji era which has a pond also with koi. https://shimabaraonsen.com/guide/shimeisou While the town itself is no cooler than Kumamoto, the abundance of water makes it feel so. The nearby sea, full of grotesque islets created by eruptions of Unzen volcano, is also a delightful place for a dip. This guide is an excellent read: https://zekkeijapan.com/article/index/705/ - William